The present invention relates to an elastic element structure for the real retention ratchet gear in magnetic tape cassettes.
As is known, in magnetic tape cassettes, in particular in so-called videocassettes, a ratchet gear is used which is constituted by a pair of ratchets oscillating about an axis substantially parallel to the axis of rotation of the reels, which are pushed elastically against a toothed flange of the reel, so as to prevent the rotation of the reels, when the cassette is not inserted in the recording or playback device, to prevent the rotation of said reels in the direction of unwinding of the tape from the reel.
Various types of elastic elements are currently used which are constituted, for example, by an elastic leaf spring having a lower flap for coupling to the cassette shell, to the side whereof two elastic arms are provided which act with a thrusting action on the thrust branches of the ratchets.
This type of solution has, first of all, the disadvantage of not allowing packaging of the elastic laminae in reels, since the presence of the small plate arranged to the side of the elastic arms does not allow the possibility of unwinding in a tape-like manner the various elastic elements.
Another disadvantage resides in the fact that the elastic preloading to be imparted to the elastic arms which thrust the ratchets must be performed, during the step of assembly of the cassette, by performing a composite movement during the insertion of the ratchets in the cassette, which slows down all the steps of automatic assembly of the cassette components.
To obviate these disadvantages, springs for videocassette ratchet gears have already been introduced which are substantially constituted by an elongated elastic lamina which is provided with a central portion, associable with the cassette structure, from which there extend two elastic arms, inclined with respect to the central portion, which act with a thrusting action against the ratchets.
This solution allows to package the various elastic elements in a continuous tape, but is not conducive to advantages regarding the elastic preloading of the laminae, which still require a composite movement of insertion of the ratchets.
To try to limit this disadvantage, ratchets have been introduced which, in their lower part of the thrust arm which engages with the elastic lamination, are provided with a bevel in the shape of an inclined plane, so that the insertion of the ratchet along the direction of oscillation of the ratchet itself creates a component which elastically compresses the elastic lamina.
This solution, though valid from many points of view, has the disadvantage of possibly creating particles which come loose from the thrust arm and may remain free within the cassette with the possibility of damage of other component elements. The elastic laminae are in fact generally obtained by punching and have burr at their free edges which may scrape the plastic material which constitutes the ratchets, removing particles of plastic which, by coming loose and remaining within the cassette, may create a severe detriment to the good quality of the cassette.